1. Field of the Invention
This invention relates to an apparatus for calculating a rotational angle or a turn angle of a moving object such as an automotive vehicle.
2. Description of the Prior Art
Some car navigation systems (automotive navigation systems) include sensors for detecting angular rates or angular velocities of car bodies (vehicle bodies). Examples of such angular-velocity sensors are fiber-optic gyroscopes, mechanical gyroscopes, and vibratory gyroscopes. Generally, the output signal of an angular-velocity sensor has offset components in addition to detected information components. To accurately derive detected information from the output signal of the angular-velocity sensor, it is necessary to cancel the offset components in the angular-velocity sensor output signal.
In a car navigation system, the amount of offset in the output signal of an angular-velocity sensor tends to be drifted by various causes. A prior-art device for canceling the signal offset can not adequately follow certain types of drift of the signal offset.